Stress-Relieved Weldment for Box Sections

ABSTRACT

A structural member, such as an excavator boom, comprises four plates forming a box section secured together at each corner thereof by a weldment comprising an L-shaped angle bar disposed within the box section and a weld which penetrates into each adjacent pair of plates and into an apex of the angle bar.

Matted States Patent [1 1 Yancey May 13, 1975 STRESS-RELIEVED WELDMENTFOR BOX SECTIONS [75] Inventor:

[73] Assignee: Caterpillar Tractor Company,

Peoria, 111.

[22] Filed: Apr. 9, 1973 [21] Appl. No.: 348,926

John W. Yancey, Aurora, 111.

Primary ExaminerFrank L. Abbott Assistant Examiner-Carl D. FriedmanAttorney, Agent, or Firm-Phillips, Moore, Weissenberger, Lempio &Strabala [57] ABSTRACT A structural member, such as an excavator boom,comprises four plates forming a box section secured together at eachcorner thereof by a weldment com prising an L-shaped angle bar disposedwithin the box section and a weld which penetrates into each adjacentpair of plates and into an apex of the angle bar.

4 Claims, 4 Drawing Figures [52] US. Cl. 52/758 B; 52/731; 29/155 C [51]Int. Cl. E04c 3/00 [58] Field of Search 52/730, 731, 732, 758 B, 52/415,433, 259, 632; 29/155 R, 155 C, 491; 138/171 [56] References CitedUNITED STATES PATENTS 2,280,150 4/1942 Hasse et a1 1. 29/491 X mzmmm i3% 3,882,654

sum 10F 2 Pmmranmwm 3.882.654

SHEET 2 (IF 2 (PRIOR ART) (PRIOR ART) STRESS-RELIEVE!) WELDMENT FOR BOXSECTIONS BACKGROUND OF THE INVENTION Box sections employed in thestructural members for heavy duty construction machines, such as theboom for a hydraulic excavator or the track roller frame for atrack-type tractor, are subjected to torsional and bending loads of highmagnitude. The box sections are normally fabricated from fourload-bearing plates which are secured together at their corners byweldments. Due to the thickness of the plates and further due to thelarge weld areas required, backup means are oftentimes provided in theweldment to insure increased structurally integrity thereat.

Such conventional backup means are illustrated in hereinafter more fullydescribed FIGS. 3 and 4 of applicants drawings which disclose aroll-formed backup bridge 16a and a single backup plate 16b,respectively. Such conventional backup means induce high stressconcentrations at the weldment and/or allow the weld to blow through theweldment, thus resulting in premature failure of the structural member.

SUMMARY OF THIS INVENTION An object of this invention is to overcome theabove, briefly described problems by providing an economical andnon-complex stress relieved weldment for the corners of a box sectionwhich exhibits a high degree of structural integrity when subjected toheavy-duty use. The weldment comprises an L-shaped angle bar having apair of legs each abutting inner surfaces of a respective member of thebox section. Common weld means secure the members and the angle bartogether.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects of this invention willbecome apparent from the following description and accompanying drawingswherein:

FIG. 1 illustrates a box section, such as the transverse cross-sectionthrough an excavator boom, a track roller frame or the like;

FIG. 2 is an enlarged view of a weldment employed at each corner of thebox section with stress concentration lines superimposed thereon; and

FIGS. 3 and 4 are views similar to FIG. 2, but illustrating conventionalweldments.

DETAILED DESCRIPTION FIG. 1 illustrates a box section of a structuralmember such as a boom employed on a hydraulic excavator, a track rollerframe for a track-type tractor or the like. As illustrated, the comersof the metallic box section are each subjected to compressive andtensional forces C and T, respectively, when torsional or bending loadsare imposed thereon. The torsional loads would normally tend to rack thebox section whereas the bending loads would normally tend to induce thesides of the box section to bulge out.

In order to counteract such tendencies, structural members or plates11-14 of the box section are provided with a stress relieved weldment 15at each corner thereof. As shown in FIG. 2, the weldment comprises anL-shaped angle bar 16 having a first leg 17 abutting inner surfaces offirst plate 1 l and a second leg 18 abutting inner surfaces oftransversely disposed and adjacent second plate 12. The edge of thesecond plate, for

example, is disposed in edge facing relationship relative to the innersurfaces of the first plate.

The angle bar may be initially tack-welded to one of the plates toprovide for the weld backup function upon application of a common weldmeans 19 thereto. In the preferred embodiment of this invention, thelegs of the angle bar are solely secured to the plates by the weld meansand are not otherwise secured to the plates to aid in the hereinaftermore fully described stress relieving function. The weld means isapplied exteriorly of the box section to have its root penetrategenerally downwardly through the lower end of plate 12, through an apex20 of the angle bar and substantially into plate 11 (preferably to adepth of from one-eighth to onethird of the thickness of plate 11).

Since apex 20 of the angle bar provides a relatively large mass ofmaterial thereat, a weld arc of high amperage will not tend to burnthrough the weldment, beneath leg 17 of the angle bar. In addition, thesubstantial length of each leg 17 and 18 (preferably at least one-halfof the thickness of an adjacent plate) eliminates weld blow-through eventhough a slight gap may form between leg 17 and plate 1 1. In thepreferred embodiment of this invention, the thickness of each leg 17 and18 is preferably selected from the range of from one-eighth to one-thirdof the thickness of each adjacent plate.

Such construction, in addition to the above described non-securance ofsubstantial portions of legs 17 and 18 to the plates, provides someflexibility at the weldment to aid in reducing stress concentrations Sthereat. Otherwise stated, an abrupt change in stiffness and geometricshape at the weldment would substantially increase such stressconcentrations thereat.

FIG. 3 illustrates a corner of a conventional box section 10a whereinplates 11a and 12a are secured together by a weld 19a. Backup means,comprising a longitudinally extending ridge 16a is roll-formed on plate11a to induce relatively high stress concentrations S FIG. 4 illustratesa corner of a second conventional box section wherein a pair of plates 11b and 12b are secured together by a weld 19b and by a single backupplate 16b. The theoretical stress concentrations are illustrated at S Agap 21 is formed at the base of plate 16b to induce weld blow-throughthrough the gap upon application of weld 19b.

It should be noted that the FIGS. 3 and 4 weldments inherently providelesser degrees of structural integrity than applicants weldment,illustrated in FIGS. 1 and 2. It should be further noted that duringfabrication of the FIG. 1 box section, that the lower end of weldment 19will tend to notch downwardly into plate 1 1, due to the low heat sinkcapability of angle bar 16.

What is claimed is:

1. A stress-relieved weldment comprising a pair of trasversely disposedfirst and second plates, with an edge of said second plate beingdisposed in edge facing relationship relative to the inner surfaces ofsaid first plate,

an L-shaped angle bar having first and second legs abutting innersurfaces of said first and second plates, respectively, the thickness ofeach of the legs of said angle bar being from one-eighth to onethird ofthe thickness of a respective one of said plates and common weld meanssecuring said plates and said angle bar together wherein said weld meanspene- 3. The weldment of claim ll wherein the length of 1 each ofsaidlegs is at least one-half of the thickness of a respectiveunderlying member.

4. The weldment 0f claim--l wherein four of said plates form arectangular box section have four corners therof each secured by a said,L-shaped angle bara'nd I a said weld means. l I

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3 ,88265 DATED May 13, 1975 INVENTOR(S) John W. Yancey It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

On the Title Page, Item [73], change the spelling of the assignee'scorporate name from "Caterpillar Tractor Company" to -CaterpillarTractor Co.---.

Signed and Sealed this twenty-eight Day Of October 1975 [S AL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Parentsand Trademarks

1. A stress-relieved weldment comprising a pair of trasversely disposedfirst and second plates, with an edge of said second plate beingdisposed in edge facing relationship relative to the inner surfaces ofsaid first plate, an L-shaped angle bar having first and second legsabutting inner surfaces of said first and second plates, respectively,the thickness of each of the legs of said angle bar being fromone-eighth to one-third of the thickness of a respective one of saidplates and common weld means securing said plates and said angle bartogether wherein said weld means penetrates through said second plateand has a root that penetrates through an apex of said angle bar,joining the first and second legs thereof together, and into said firstplate.
 2. The weldment of claim 1 wherein the root of said weld meanspenetrates into said first plate at a depth which is from one-eighth toone-third of the thickness of said first plate.
 3. The weldment of claim1 wherein the length of each of said legs is At least one-half of thethickness of a respective underlying member.
 4. The weldment of claim 1wherein four of said plates form a rectangular box section have fourcorners therof each secured by a said, L-shaped angle bar and a saidweld means.